In a mobile communication system, a cell is formed as a range in which a radio base station and a mobile station such as a cellular phone can perform transmission and reception. Further, a plurality of the cells is combined and a communicable range covers a wide area. In such a communication system, the mobile station continues communication while switching the radio base station, which the mobile station communicates with, according to movement. A system of the communication system explained above is called a cellular system.
Currently, a service of a third generation mobile communication system by a Wideband Code Division Multiple Access (W-CDMA) or Code Division Multiple Access (CDMA) system is performed. High Speed Downlink Packet Access (HSDPA), which is a downlink high-speed transmission technology, and High Speed Uplink Packet Access (HSUPA), which is an uplink high-speed transmission technology, are proposed. High Speed Packet Access (HSPA) obtained by combining these technologies, HSPA+, which is an advanced system of the HSPA, and the like are proposed. On the other hand, examination of a next generation mobile communication system, which enables higher-speed communication, is underway.
In the 3rd Generation Partnership Project (3GPP), examination of LTE-advanced, which is an advanced version of Long Term Evolution (LTE) started to be in service around 2010 is performed targeting a service start around 2015 (see, for example, Non-Patent document 1 and Non-Patent document 2).